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    <title>Document</title>
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    <script>

        // 接收用户输入的分数，根据分数输出对应的等级字母 A、B、C、D、E。
        let fraction = +prompt('请输入您的分数')

        if(fraction >= 90) {
            document.write('A');
        } else if(fraction >= 80 && fraction < 90) {
            document.write('B');
        } else if(fraction >= 70 && fraction < 80) {
            document.write('C');
        } else if(fraction >= 60 && fraction < 70) {
            document.write('D');
        } else {
            document.write('E');
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